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Special Issue "Green Chemistry and the Biorefinery"

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Green Chemistry".

Deadline for manuscript submissions: closed (31 March 2015).

Special Issue Editors

Guest Editor
Prof. James H. Clark

Green Chemistry Centre of Excellence, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
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Interests: green chemistry; heterogeneous catalysis; circular economy
Guest Editor
Dr. Thomas J. Farmer

Green Chemistry Centre of Excellence, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
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Interests: green chemistry; polymer recycling; clean synthesis; bio-based polymers
Guest Editor
Dr. Andrew J. Hunt

Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
Website | E-Mail
Interests: natural and bio-derived solvents; organic chemistry, product cleaning, material development, impregnation and utilisation of computer models to predict the effects of solvents in chemical reactions

Special Issue Information

Dear Colleagues,

The environmental impacts of the chemical industry and maintaining access to resources required to support that industry are two major challenges of the 21st Century. The use of sustainable bio-based resources, and subsequent conversion to bio-based products, requires the use of biorefineries. However, this conversion also needs the synergistic application of green chemistry, ensuring the technologies used within the biorefinery limit environmental impact, avoid the use of depleting elements and strives to minimise waste produced. Likewise, the greening of chemical processes will not be fully implemented until all feedstocks are sustainably derived, including the use of bio-derived solvents, catalysts and auxiliaries where required. This Special Issue will highlight where green chemistry must be applied for production within biorefineries and will likewise demonstrate where chemicals and materials produced from biorefineries have been used for green chemical processes. Both green chemistry and biorefineries require one another to operate in a fully sustainable, circular and environmentally friendly chemical industry needed in centuries to come.

Prof. James H Clark
Dr. Thomas J Farmer
Dr. Andrew J. Hunt
Guest Editors

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Keywords

  • green chemistry
  • biorefinery
  • bio-based chemicals
  • biomass to chemicals
  • sustainable chemicals
  • clean synthesis

Published Papers (21 papers)

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Research

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Open AccessArticle
Economic Assessment of Supercritical CO2 Extraction of Waxes as Part of a Maize Stover Biorefinery
Int. J. Mol. Sci. 2015, 16(8), 17546-17564; https://doi.org/10.3390/ijms160817546
Received: 1 June 2015 / Revised: 14 July 2015 / Accepted: 24 July 2015 / Published: 31 July 2015
Cited by 15 | PDF Full-text (1192 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
To date limited work has focused on assessing the economic viability of scCO2 extraction to obtain waxes as part of a biorefinery. This work estimates the economic costs for wax extraction from maize stover. The cost of manufacture (COM) for [...] Read more.
To date limited work has focused on assessing the economic viability of scCO2 extraction to obtain waxes as part of a biorefinery. This work estimates the economic costs for wax extraction from maize stover. The cost of manufacture (COM) for maize stover wax extraction was found to be €88.89 per kg of wax, with the fixed capital investment (FCI) and utility costs (CUT) contributing significantly to the COM. However, this value is based solely on scCO2 extraction of waxes and does not take into account the downstream processing of the biomass following extraction. The cost of extracting wax from maize stover can be reduced by utilizing pelletized leaves and combusting the residual biomass to generate electricity. This would lead to an overall cost of €10.87 per kg of wax (based on 27% combustion efficiency for electricity generation) and €4.56 per kg of wax (based on 43% combustion efficiency for electricity generation). A sensitivity analysis study showed that utility costs (cost of electricity) had the greatest effect on the COM. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessArticle
Synthesis of Unsaturated Polyester Resins from Various Bio-Derived Platform Molecules
Int. J. Mol. Sci. 2015, 16(7), 14912-14932; https://doi.org/10.3390/ijms160714912
Received: 5 May 2015 / Revised: 10 June 2015 / Accepted: 10 June 2015 / Published: 2 July 2015
Cited by 43 | PDF Full-text (1579 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Utilisation of bio-derived platform molecules in polymer synthesis has advantages which are, broadly, twofold; to digress from crude oil dependence of the polymer industry and secondly to reduce the environmental impact of the polymer synthesis through the inherent functionality of the bio-derived platform [...] Read more.
Utilisation of bio-derived platform molecules in polymer synthesis has advantages which are, broadly, twofold; to digress from crude oil dependence of the polymer industry and secondly to reduce the environmental impact of the polymer synthesis through the inherent functionality of the bio-derived platform molecules. Bulk polymerisation of bio-derived unsaturated di-acids has been employed to produce unsaturated polyester (UPEs) which have been analysed by GPC, TGA, DSC and NMR spectroscopy, advancing on the analysis previously reported. UPEs from the diesters of itaconic, succinic, and fumaric acids were successfully synthesised with various diols and polyols to afford resins of MN 480–477,000 and Tg of −30.1 to −16.6 °C with solubilities differing based on starting monomers. This range of properties allows for many applications and importantly due to the surviving Michael acceptor moieties, solubility and cross-linking can be specifically tailored, post polymerisation, to the desired function. An improved synthesis of itaconate and succinate co-polymers, via the initial formation of an itaconate bis-diol, is also demonstrated for the first time, resulting in significantly improved itaconate incorporation. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessArticle
Bacterial Cellulose Production from Industrial Waste and by-Product Streams
Int. J. Mol. Sci. 2015, 16(7), 14832-14849; https://doi.org/10.3390/ijms160714832
Received: 8 April 2015 / Revised: 8 June 2015 / Accepted: 11 June 2015 / Published: 1 July 2015
Cited by 60 | PDF Full-text (3000 KB) | HTML Full-text | XML Full-text
Abstract
The utilization of fermentation media derived from waste and by-product streams from biodiesel and confectionery industries could lead to highly efficient production of bacterial cellulose. Batch fermentations with the bacterial strain Komagataeibacter sucrofermentans DSM (Deutsche Sammlung von Mikroorganismen) 15973 were initially carried out [...] Read more.
The utilization of fermentation media derived from waste and by-product streams from biodiesel and confectionery industries could lead to highly efficient production of bacterial cellulose. Batch fermentations with the bacterial strain Komagataeibacter sucrofermentans DSM (Deutsche Sammlung von Mikroorganismen) 15973 were initially carried out in synthetic media using commercial sugars and crude glycerol. The highest bacterial cellulose concentration was achieved when crude glycerol (3.2 g/L) and commercial sucrose (4.9 g/L) were used. The combination of crude glycerol and sunflower meal hydrolysates as the sole fermentation media resulted in bacterial cellulose production of 13.3 g/L. Similar results (13 g/L) were obtained when flour-rich hydrolysates produced from confectionery industry waste streams were used. The properties of bacterial celluloses developed when different fermentation media were used showed water holding capacities of 102–138 g·water/g·dry bacterial cellulose, viscosities of 4.7–9.3 dL/g, degree of polymerization of 1889.1–2672.8, stress at break of 72.3–139.5 MPa and Young’s modulus of 0.97–1.64 GPa. This study demonstrated that by-product streams from the biodiesel industry and waste streams from confectionery industries could be used as the sole sources of nutrients for the production of bacterial cellulose with similar properties as those produced with commercial sources of nutrients. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessArticle
Chitosan Derivatives as Important Biorefinery Intermediates. Quaternary Tetraalkylammonium Chitosan Derivatives Utilized in Anion Exchange Chromatography for Perchlorate Removal
Int. J. Mol. Sci. 2015, 16(5), 9064-9077; https://doi.org/10.3390/ijms16059064
Received: 30 March 2015 / Revised: 15 April 2015 / Accepted: 16 April 2015 / Published: 23 April 2015
Cited by 5 | PDF Full-text (1579 KB) | HTML Full-text | XML Full-text
Abstract
There has recently been great interest in the valorization of biomass waste in the context of the biorefinery. The biopolymer chitosan, derived from chitin, is present in large quantities of crustacean waste. This biomass can be converted into value-added products with applications in [...] Read more.
There has recently been great interest in the valorization of biomass waste in the context of the biorefinery. The biopolymer chitosan, derived from chitin, is present in large quantities of crustacean waste. This biomass can be converted into value-added products with applications in energy, fuel, chemicals and materials manufacturing. The many reported applications of this polymer can be attributed to its unique properties, such as biocompatibility, chemical versatility, biodegradability and low toxicity. Cost effective water filters which decontaminate water by removal of specific impurities and microbes are in great demand. To address this need, the development of ion exchange resins using environmentally friendly, renewable materials such as biopolymers as solid supports was evaluated. The identification and remediation of perchlorate contaminated water using an easy, inexpensive method has come under the spotlight recently. Similarly, the use of a low cost perchlorate selective solid phase extraction (SPE) cartridge that can be rapidly employed in the field is desirable. Chitosan based SPE coupled with colorimetric analytical methods showed promise as a renewable anion exchange support for perchlorate analysis or removal. The polymers displayed perchlorate retention comparable to the commercial standard whereby the quaternized iron loaded polymer TMC-Fe(III) displayed the best activity. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessArticle
Processed vs. Non-Processed Biowastes for Agriculture: Effects of Post-Harvest Tomato Plants and Biochar on Radish Growth, Chlorophyll Content and Protein Production
Int. J. Mol. Sci. 2015, 16(4), 8826-8843; https://doi.org/10.3390/ijms16048826
Received: 21 March 2015 / Revised: 9 April 2015 / Accepted: 14 April 2015 / Published: 21 April 2015
Cited by 14 | PDF Full-text (913 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this work was to address the issue of processed vs. non-processed biowastes for agriculture, by comparing materials widely differing for the amount of process energy consumption. Thus, residual post harvest tomato plants (TP), the TP hydrolysates obtained at pH 13 [...] Read more.
The aim of this work was to address the issue of processed vs. non-processed biowastes for agriculture, by comparing materials widely differing for the amount of process energy consumption. Thus, residual post harvest tomato plants (TP), the TP hydrolysates obtained at pH 13 and 60 °C, and two known biochar products obtained by 650 °C pyrolysis were prepared. All products were characterized and used in a cultivation of radish plants. The chemical composition and molecular nature of the materials was investigated by solid state 13C NMR spectrometry, elemental analysis and potentiometric titration. The plants were analysed for growth and content of chlorophyll, carotenoids and soluble proteins. The results show that the TP and the alkaline hydrolysates contain lignin, hemicellulose, protein, peptide and/or amino acids moieties, and several mineral elements. The biochar samples contain also similar mineral elements, but the organic fraction is characterized mainly by fused aromatic rings. All materials had a positive effect on radish growth, mainly on the diameter of roots. The best performances in terms of plant growth were given by miscanthus originated biochar and TP. The most significant effect was the enhancement of soluble protein content in the plants treated with the lowest energy consumption non processed TP. The significance of these findings for agriculture and the environment is discussed. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessArticle
Chemicals from Agave sisalana Biomass: Isolation and Identification
Int. J. Mol. Sci. 2015, 16(4), 8761-8771; https://doi.org/10.3390/ijms16048761
Received: 23 March 2015 / Revised: 11 April 2015 / Accepted: 13 April 2015 / Published: 20 April 2015
Cited by 12 | PDF Full-text (927 KB) | HTML Full-text | XML Full-text
Abstract
Agave sisalana (sisal) is known worldwide as a source of hard fibers, and Brazil is the largest producer of sisal. Nonetheless, the process of removing the fibers of the sisal leaf generates 95% waste. In this study, we applied chemical sequential steps (hydrothermal [...] Read more.
Agave sisalana (sisal) is known worldwide as a source of hard fibers, and Brazil is the largest producer of sisal. Nonetheless, the process of removing the fibers of the sisal leaf generates 95% waste. In this study, we applied chemical sequential steps (hydrothermal extraction, precipitation, liquid-liquid extraction, crystallization, SiO2 and Sephadex LH 20 column chromatography) to obtain pectin, mannitol, succinic acid, kaempferol and a mixture of saponins as raw chemicals from sisal biomass. The structural identification of these compounds was performed though spectrometric methods, such as Infrared (IR), Ultraviolet (UV), Mass spectrometry (MS) and Nuclear magnetic resonance (NMR). All the sisal chemicals found in this work are used by both the chemical and pharmaceutical industries as excipients or active principles in products. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessArticle
Alternative Bio-Based Solvents for Extraction of Fat and Oils: Solubility Prediction, Global Yield, Extraction Kinetics, Chemical Composition and Cost of Manufacturing
Int. J. Mol. Sci. 2015, 16(4), 8430-8453; https://doi.org/10.3390/ijms16048430
Received: 26 February 2015 / Revised: 6 April 2015 / Accepted: 9 April 2015 / Published: 15 April 2015
Cited by 42 | PDF Full-text (2460 KB) | HTML Full-text | XML Full-text
Abstract
The present study was designed to evaluate the performance of alternative bio-based solvents, more especially 2-methyltetrahydrofuran, obtained from crop’s byproducts for the substitution of petroleum solvents such as hexane in the extraction of fat and oils for food (edible oil) and non-food (bio [...] Read more.
The present study was designed to evaluate the performance of alternative bio-based solvents, more especially 2-methyltetrahydrofuran, obtained from crop’s byproducts for the substitution of petroleum solvents such as hexane in the extraction of fat and oils for food (edible oil) and non-food (bio fuel) applications. First a solvent selection as well as an evaluation of the performance was made with Hansen Solubility Parameters and the COnductor-like Screening MOdel for Realistic Solvation (COSMO-RS) simulations. Experiments were performed on rapeseed oil extraction at laboratory and pilot plant scale for the determination of lipid yields, extraction kinetics, diffusion modeling, and complete lipid composition in term of fatty acids and micronutrients (sterols, tocopherols and tocotrienols). Finally, economic and energetic evaluations of the process were conducted to estimate the cost of manufacturing using 2-methyltetrahydrofuran (MeTHF) as alternative solvent compared to hexane as petroleum solvent. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessArticle
Organocatalytic Upgrading of Furfural and 5-Hydroxymethyl Furfural to C10 and C12 Furoins with Quantitative Yield and Atom-Efficiency
Int. J. Mol. Sci. 2015, 16(4), 7143-7158; https://doi.org/10.3390/ijms16047143
Received: 13 February 2015 / Revised: 25 March 2015 / Accepted: 26 March 2015 / Published: 30 March 2015
Cited by 16 | PDF Full-text (1141 KB) | HTML Full-text | XML Full-text
Abstract
There is increasing interest in the upgrading of C5 furfural (FF) and C6 5-hydroxymethyl furfural (HMF) into C10 and C12 furoins as higher energy-density intermediates for renewable chemicals, materials, and biofuels. This work utilizes the organocatalytic approach, using the [...] Read more.
There is increasing interest in the upgrading of C5 furfural (FF) and C6 5-hydroxymethyl furfural (HMF) into C10 and C12 furoins as higher energy-density intermediates for renewable chemicals, materials, and biofuels. This work utilizes the organocatalytic approach, using the in situ generated N,S-heterocyclic carbene catalyst derived from thiazolium ionic liquids (ILs), to achieve highly efficient self-coupling reactions of FF and HMF. Specifically, variations of the thiazolium IL structure have led to the most active and efficient catalyst system of the current series, which is derived from a new thiazolium IL carrying the electron-donating acetate group at the 5-ring position. For FF coupling by this IL (0.1 mol %, 60 °C, 1 h), when combined with Et3N, furoin was obtained in >99% yield. A 97% yield of the C12 furoin was also achieved from the HMF coupling by this catalyst system (10 mol % loading, 120 °C, 3 h). On the other hand, the thiazolium IL bearing the electron-withdrawing group at the 5-ring position is the least active and efficient catalyst. The mechanistic aspects of the coupling reaction by the thiazolium catalyst system have also been examined and a mechanism has been proposed. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessArticle
Protease and Hemicellulase Assisted Extraction of Dietary Fiber from Wastes of Cynara cardunculus
Int. J. Mol. Sci. 2015, 16(3), 6057-6075; https://doi.org/10.3390/ijms16036057
Received: 4 February 2015 / Revised: 3 March 2015 / Accepted: 10 March 2015 / Published: 16 March 2015
Cited by 5 | PDF Full-text (740 KB) | HTML Full-text | XML Full-text
Abstract
The action of protease and hemicellulase for the extraction of fractions enriched in soluble fiber from bracts and stems of Cynara cardunculus was evaluated. Using a two-factor simplex design comprising protease amounts of 0–200 μL and hemicellulase amounts of 0–200 mg for 5 [...] Read more.
The action of protease and hemicellulase for the extraction of fractions enriched in soluble fiber from bracts and stems of Cynara cardunculus was evaluated. Using a two-factor simplex design comprising protease amounts of 0–200 μL and hemicellulase amounts of 0–200 mg for 5 g of material, we explored the effect of a 5 h enzymatic treatment at 40 °C on the chemical composition and yield of the fractions isolated. The fractions contained inulin and pectin. In general, the protein, inulin, and polyphenol contents and also the yields were higher for fractions obtained from stems. The most marked effects were observed when enzymes were used at higher concentrations, especially for hemicellulase. The inclusion of a pre-heating step increased the yield and the inulin content for fractions isolated from bracts and stems and decreased the protein and polyphenol contents, and the galacturonic acid for bracts. These fractions, in general, contained the polyphenolic compounds monocaffeoylquinic acid, apigenin, and pinoresinol. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessArticle
Cultivation of Chlorella vulgaris and Arthrospira platensis with Recovered Phosphorus from Wastewater by Means of Zeolite Sorption
Int. J. Mol. Sci. 2015, 16(2), 4250-4264; https://doi.org/10.3390/ijms16024250
Received: 21 December 2014 / Revised: 3 February 2015 / Accepted: 10 February 2015 / Published: 16 February 2015
Cited by 14 | PDF Full-text (791 KB) | HTML Full-text | XML Full-text
Abstract
In this study, zeolite was employed for the separation and recovery of P from synthetic wastewater and its use as phosphorus (P) source for the cultivation of the green microalga Chlorella vulgaris and the cyanobacterium Arthrospira (Spirulina) platensis. At P-loaded zeolite concentration [...] Read more.
In this study, zeolite was employed for the separation and recovery of P from synthetic wastewater and its use as phosphorus (P) source for the cultivation of the green microalga Chlorella vulgaris and the cyanobacterium Arthrospira (Spirulina) platensis. At P-loaded zeolite concentration of 0.15–1 g/L, in which P was limited, the two species displayed quite different behavior regarding their growth and biomass composition. C. vulgaris preferred to increase the intracellular P and did not synthesize biomass, while A. platensis synthesized biomass keeping the intracellular P as low as possible. In addition under P limitation, C. vulgaris did display some little alteration of the biomass composition, while A. platensis did it significantly, accumulating carbohydrates around 70% from about 15%–20% (control). Both species could desorb P from zeolite biologically. A. platensis could recover over 65% and C. vulgaris 25% of the P bounded onto zeolite. When P-loaded zeolite concentration increased to 5 g/L, P was adequate to support growth for both species. Especially in the case of C. vulgaris, growth was stimulated from the presence of P-loaded zeolite and produced more biomass compared to the control. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessArticle
Thermochemical Pretreatments of Organic Fraction of Municipal Solid Waste from a Mechanical-Biological Treatment Plant
Int. J. Mol. Sci. 2015, 16(2), 3769-3782; https://doi.org/10.3390/ijms16023769
Received: 27 November 2014 / Accepted: 28 January 2015 / Published: 9 February 2015
Cited by 7 | PDF Full-text (1092 KB) | HTML Full-text | XML Full-text
Abstract
The organic fraction of municipal solid waste (OFMSW) usually contains high lignocellulosic and fatty fractions. These fractions are well-known to be a hard biodegradable substrate for biological treatments and its presence involves limitations on the performance of anaerobic processes. To avoid this, thermochemical [...] Read more.
The organic fraction of municipal solid waste (OFMSW) usually contains high lignocellulosic and fatty fractions. These fractions are well-known to be a hard biodegradable substrate for biological treatments and its presence involves limitations on the performance of anaerobic processes. To avoid this, thermochemical pretreatments have been applied on the OFMSW coming from a full-scale mechanical-biological treatment (MBT) plant, in order to pre-hydrolyze the waste and improve the organic matter solubilisation. To study the solubilisation yield, the increments of soluble organic matter have been measured in terms of dissolved organic carbon (DOC), soluble chemical oxygen demand (sCOD), total volatile fatty acids (TVFA) and acidogenic substrate as carbon (ASC). The process variables analyzed were temperature, pressure and NaOH dosage. The levels of work for each variable were three: 160–180–200 °C, 3.5–5.0–6.5 bar and 2–3–4 g NaOH/L. In addition, the pretreatment time was also modified among 15 and 120 min. The best conditions for organic matter solubilisation were 160 °C, 3 g NaOH/L, 6.5 bar and 30 min, with yields in terms of DOC, sCOD, TVFA and ASC of 176%, 123%, 119% and 178% respectively. Thus, predictably the application of this pretreatment in these optimum conditions could improve the H2 production during the subsequent Dark Fermentation process. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessArticle
Chemical Modeling of Acid-Base Properties of Soluble Biopolymers Derived from Municipal Waste Treatment Materials
Int. J. Mol. Sci. 2015, 16(2), 3405-3418; https://doi.org/10.3390/ijms16023405
Received: 23 December 2014 / Revised: 22 January 2015 / Accepted: 29 January 2015 / Published: 4 February 2015
Cited by 2 | PDF Full-text (947 KB) | HTML Full-text | XML Full-text
Abstract
This work reports a study of the proton-binding capacity of biopolymers obtained from different materials supplied by a municipal biowaste treatment plant located in Northern Italy. One material was the anaerobic fermentation digestate of the urban wastes organic humid fraction. The others were [...] Read more.
This work reports a study of the proton-binding capacity of biopolymers obtained from different materials supplied by a municipal biowaste treatment plant located in Northern Italy. One material was the anaerobic fermentation digestate of the urban wastes organic humid fraction. The others were the compost of home and public gardening residues and the compost of the mix of the above residues, digestate and sewage sludge. These materials were hydrolyzed under alkaline conditions to yield the biopolymers by saponification. The biopolymers were characterized by 13C NMR spectroscopy, elemental analysis and potentiometric titration. The titration data were elaborated to attain chemical models for interpretation of the proton-binding capacity of the biopolymers obtaining the acidic sites concentrations and their protonation constants. The results obtained with the models and by NMR spectroscopy were elaborated together in order to better characterize the nature of the macromolecules. The chemical nature of the biopolymers was found dependent upon the nature of the sourcing materials. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessArticle
Efficient Production of the Flavoring Agent Zingerone and of both (R)- and (S)-Zingerols via Green Fungal Biocatalysis. Comparative Antifungal Activities between Enantiomers
Int. J. Mol. Sci. 2014, 15(12), 22042-22058; https://doi.org/10.3390/ijms151222042
Received: 8 October 2014 / Revised: 11 November 2014 / Accepted: 12 November 2014 / Published: 1 December 2014
Cited by 1 | PDF Full-text (1334 KB) | HTML Full-text | XML Full-text
Abstract
Zingerone (1) and both chiral forms of zingerol (2) were obtained from dehydrozingerone (3) by biotransformation with filamentous fungi. The bioconversion of 3 with A. fumigatus, G. candidum or R. oryzae allowed the production of 1 [...] Read more.
Zingerone (1) and both chiral forms of zingerol (2) were obtained from dehydrozingerone (3) by biotransformation with filamentous fungi. The bioconversion of 3 with A. fumigatus, G. candidum or R. oryzae allowed the production of 1 as the sole product at 8 h and in 81%–90% at 72 h. In turn, A. flavus, A. niger, C. echinulata, M. circinelloides and P. citrinum produced 1 at 8 h, but at 72 h alcohol 2 was obtained as the major product (74%–99%). Among them, A. niger and M. circinelloides led to the anti-Prelog zingerol (R)-2 in only one step with high conversion rates and ee. Instead, C. echinulata and P. citrinum allowed to obtain (S)-2 in only one step, with high conversion rates and ee. Both chiral forms of 2 were tested for antifungal properties against a panel of clinically important fungi, showing that (R)-, but not (S)-2 possessed antifungal activity. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessArticle
Boric Ester-Type Molten Salt via Dehydrocoupling Reaction
Int. J. Mol. Sci. 2014, 15(11), 21080-21089; https://doi.org/10.3390/ijms151121080
Received: 17 September 2014 / Revised: 5 November 2014 / Accepted: 6 November 2014 / Published: 14 November 2014
Cited by 1 | PDF Full-text (1256 KB) | HTML Full-text | XML Full-text
Abstract
Novel boric ester-type molten salt was prepared using 1-(2-hydroxyethyl)-3-methylimidazolium chloride as a key starting material. After an ion exchange reaction of 1-(2-hydroxyethyl)-3-methylimidazolium chloride with lithium (bis-(trifluoromethanesulfonyl) imide) (LiNTf2), the resulting 1-(2-hydroxyethyl)-3-methylimidazolium NTf2 was reacted with 9-borabicyclo[3.3.1]nonane (9-BBN) to [...] Read more.
Novel boric ester-type molten salt was prepared using 1-(2-hydroxyethyl)-3-methylimidazolium chloride as a key starting material. After an ion exchange reaction of 1-(2-hydroxyethyl)-3-methylimidazolium chloride with lithium (bis-(trifluoromethanesulfonyl) imide) (LiNTf2), the resulting 1-(2-hydroxyethyl)-3-methylimidazolium NTf2 was reacted with 9-borabicyclo[3.3.1]nonane (9-BBN) to give the desired boric ester-type molten salt in a moderate yield. The structure of the boric ester-type molten salt was supported by 1H-, 13C-, 11B- and 19F-NMR spectra. In the presence of two different kinds of lithium salts, the matrices showed an ionic conductivity in the range of 1.1 × 10−4–1.6 × 10−5 S cm−1 at 51 °C. This was higher than other organoboron molten salts ever reported. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessArticle
Control of Several Emissions during Olive Pomace Thermal Degradation
Int. J. Mol. Sci. 2014, 15(10), 18349-18361; https://doi.org/10.3390/ijms151018349
Received: 10 July 2014 / Revised: 5 September 2014 / Accepted: 24 September 2014 / Published: 13 October 2014
Cited by 2 | PDF Full-text (2351 KB) | HTML Full-text | XML Full-text
Abstract
Biomass plays an important role as an energy source, being an interesting alternative to fossil fuels due to its environment-friendly and sustainable characteristics. However, due to the exposure of customers to emissions during biomass heating, evolved pollutants should be taken into account and [...] Read more.
Biomass plays an important role as an energy source, being an interesting alternative to fossil fuels due to its environment-friendly and sustainable characteristics. However, due to the exposure of customers to emissions during biomass heating, evolved pollutants should be taken into account and controlled. Changing raw materials or mixing them with another less pollutant biomass could be a suitable step to reduce pollution. This work studied the thermal behaviour of olive pomace, pyrenean oak and their blends under combustion using thermogravimetric analysis. It was possible to monitor the emissions released during the process by coupling mass spectrometry analysis. The experiments were carried out under non-isothermal conditions at the temperature range 25–750 °C and a heating rate of 20 °C·min−1. The following species were analysed: aromatic compounds (benzene and toluene), sulphur emissions (sulphur dioxide), 1,4-dioxin, hydrochloric acid, carbon dioxide and nitrogen oxides. The results indicated that pollutants were mainly evolved in two different stages, which are related to the thermal degradation steps. Thus, depending on the pollutant and raw material composition, different emission profiles were observed. Furthermore, intensity of the emission profiles was related, in some cases, to the composition of the precursor. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Review

Jump to: Research, Other

Open AccessReview
Opportunities for Bio-Based Solvents Created as Petrochemical and Fuel Products Transition towards Renewable Resources
Int. J. Mol. Sci. 2015, 16(8), 17101-17159; https://doi.org/10.3390/ijms160817101
Received: 22 June 2015 / Revised: 16 July 2015 / Accepted: 17 July 2015 / Published: 28 July 2015
Cited by 61 | PDF Full-text (5263 KB) | HTML Full-text | XML Full-text
Abstract
The global bio-based chemical market is growing in size and importance. Bio-based solvents such as glycerol and 2-methyltetrahydrofuran are often discussed as important introductions to the conventional repertoire of solvents. However adoption of new innovations by industry is typically slow. Therefore it might [...] Read more.
The global bio-based chemical market is growing in size and importance. Bio-based solvents such as glycerol and 2-methyltetrahydrofuran are often discussed as important introductions to the conventional repertoire of solvents. However adoption of new innovations by industry is typically slow. Therefore it might be anticipated that neoteric solvent systems (e.g., ionic liquids) will remain niche, while renewable routes to historically established solvents will continue to grow in importance. This review discusses bio-based solvents from the perspective of their production, identifying suitable feedstocks, platform molecules, and relevant product streams for the sustainable manufacturing of conventional solvents. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessReview
New Biofuel Alternatives: Integrating Waste Management and Single Cell Oil Production
Int. J. Mol. Sci. 2015, 16(5), 9385-9405; https://doi.org/10.3390/ijms16059385
Received: 26 February 2015 / Revised: 26 February 2015 / Accepted: 14 April 2015 / Published: 24 April 2015
Cited by 21 | PDF Full-text (886 KB) | HTML Full-text | XML Full-text
Abstract
Concerns about greenhouse gas emissions have increased research efforts into alternatives in bio-based processes. With regard to transport fuel, bioethanol and biodiesel are still the main biofuels used. It is expected that future production of these biofuels will be based on processes using [...] Read more.
Concerns about greenhouse gas emissions have increased research efforts into alternatives in bio-based processes. With regard to transport fuel, bioethanol and biodiesel are still the main biofuels used. It is expected that future production of these biofuels will be based on processes using either non-food competing biomasses, or characterised by low CO2 emissions. Many microorganisms, such as microalgae, yeast, bacteria and fungi, have the ability to accumulate oils under special culture conditions. Microbial oils might become one of the potential feed-stocks for biodiesel production in the near future. The use of these oils is currently under extensive research in order to reduce production costs associated with the fermentation process, which is a crucial factor to increase economic feasibility. An important way to reduce processing costs is the use of wastes as carbon sources. The aim of the present review is to describe the main aspects related to the use of different oleaginous microorganisms for lipid production and their performance when using bio-wastes. The possibilities for combining hydrogen (H2) and lipid production are also explored in an attempt for improving the economic feasibility of the process. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessReview
Economically Viable Components from Jerusalem Artichoke (Helianthus tuberosus L.) in a Biorefinery Concept
Int. J. Mol. Sci. 2015, 16(4), 8997-9016; https://doi.org/10.3390/ijms16048997
Received: 25 March 2015 / Revised: 16 April 2015 / Accepted: 17 April 2015 / Published: 22 April 2015
Cited by 20 | PDF Full-text (763 KB) | HTML Full-text | XML Full-text
Abstract
Biorefinery applications are receiving growing interest due to climatic and waste disposal issues and lack of petroleum resources. Jerusalem artichoke (Helianthus tuberosus L.) is suitable for biorefinery applications due to high biomass production and limited cultivation requirements. This paper focuses on the [...] Read more.
Biorefinery applications are receiving growing interest due to climatic and waste disposal issues and lack of petroleum resources. Jerusalem artichoke (Helianthus tuberosus L.) is suitable for biorefinery applications due to high biomass production and limited cultivation requirements. This paper focuses on the potential of Jerusalem artichoke as a biorefinery crop and the most viable products in such a case. The carbohydrates in the tubers were found to have potential for production of platform chemicals, e.g., succinic acid. However, economic analysis showed that production of platform chemicals as a single product was too expensive to be competitive with petrochemically produced sugars. Therefore, production of several products from the same crop is a must. Additional products are protein based ones from tubers and leaves and biogas from residues, although both are of low value and amount. High bioactive activity was found in the young leaves of the crop, and the sesquiterpene lactones are of specific interest, as other compounds from this group have shown inhibitory effects on several human diseases. Thus, future focus should be on understanding the usefulness of small molecules, to develop methods for their extraction and purification and to further develop sustainable and viable methods for the production of platform chemicals. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessReview
Potential Biological Applications of Bio-Based Anacardic Acids and Their Derivatives
Int. J. Mol. Sci. 2015, 16(4), 8569-8590; https://doi.org/10.3390/ijms16048569
Received: 14 March 2015 / Revised: 8 April 2015 / Accepted: 9 April 2015 / Published: 16 April 2015
Cited by 38 | PDF Full-text (846 KB) | HTML Full-text | XML Full-text
Abstract
Cashew nut shells (CNS), which are agro wastes from cashew nut processing factories, have proven to be among the most versatile bio-based renewable materials in the search for functional materials and chemicals from renewable resources. CNS are produced in the cashew nut processing [...] Read more.
Cashew nut shells (CNS), which are agro wastes from cashew nut processing factories, have proven to be among the most versatile bio-based renewable materials in the search for functional materials and chemicals from renewable resources. CNS are produced in the cashew nut processing process as waste, but they contain cashew nut shell liquid (CNSL) up to about 30–35 wt. % of the nut shell weight depending on the method of extraction. CNSL is a mixture of anacardic acid, cardanol, cardol, and methyl cardol, and the structures of these phenols offer opportunities for the development of diverse products. For anacardic acid, the combination of phenolic, carboxylic, and a 15-carbon alkyl side chain functional group makes it attractive in biological applications or as a synthon for the synthesis of a multitude of bioactive compounds. Anacardic acid, which is about 65% of a CNSL mixture, can be extracted from the agro waste. This shows that CNS waste can be used to extract useful chemicals and thus provide alternative green sources of chemicals, apart from relying only on the otherwise declining petroleum based sources. This paper reviews the potential of anacardic acids and their semi-synthetic derivatives for antibacterial, antitumor, and antioxidant activities. The review focuses on natural anacardic acids from CNS and other plants and their semi-synthetic derivatives as possible lead compounds in medicine. In addition, the use of anacardic acid as a starting material for the synthesis of various biologically active compounds and complexes is reported. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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Open AccessReview
Extrusion Pretreatment of Lignocellulosic Biomass: A Review
Int. J. Mol. Sci. 2014, 15(10), 18967-18984; https://doi.org/10.3390/ijms151018967
Received: 27 August 2014 / Revised: 23 September 2014 / Accepted: 8 October 2014 / Published: 20 October 2014
Cited by 52 | PDF Full-text (687 KB) | HTML Full-text | XML Full-text
Abstract
Bioconversion of lignocellulosic biomass to bioethanol has shown environmental, economic and energetic advantages in comparison to bioethanol produced from sugar or starch. However, the pretreatment process for increasing the enzymatic accessibility and improving the digestibility of cellulose is hindered by many physical-chemical, structural [...] Read more.
Bioconversion of lignocellulosic biomass to bioethanol has shown environmental, economic and energetic advantages in comparison to bioethanol produced from sugar or starch. However, the pretreatment process for increasing the enzymatic accessibility and improving the digestibility of cellulose is hindered by many physical-chemical, structural and compositional factors, which make these materials difficult to be used as feedstocks for ethanol production. A wide range of pretreatment methods has been developed to alter or remove structural and compositional impediments to (enzymatic) hydrolysis over the last few decades; however, only a few of them can be used at commercial scale due to economic feasibility. This paper will give an overview of extrusion pretreatment for bioethanol production with a special focus on twin-screw extruders. An economic assessment of this pretreatment is also discussed to determine its feasibility for future industrial cellulosic ethanol plant designs. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)

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Techno-Economic Evaluation of Biodiesel Production from Waste Cooking Oil—A Case Study of Hong Kong
Int. J. Mol. Sci. 2015, 16(3), 4362-4371; https://doi.org/10.3390/ijms16034362
Received: 1 January 2015 / Revised: 11 February 2015 / Accepted: 13 February 2015 / Published: 18 February 2015
Cited by 34 | PDF Full-text (734 KB) | HTML Full-text | XML Full-text
Abstract
Fossil fuel shortage is a major challenge worldwide. Therefore, research is currently underway to investigate potential renewable energy sources. Biodiesel is one of the major renewable energy sources that can be obtained from oils and fats by transesterification. However, biodiesel obtained from vegetable [...] Read more.
Fossil fuel shortage is a major challenge worldwide. Therefore, research is currently underway to investigate potential renewable energy sources. Biodiesel is one of the major renewable energy sources that can be obtained from oils and fats by transesterification. However, biodiesel obtained from vegetable oils as feedstock is expensive. Thus, an alternative and inexpensive feedstock such as waste cooking oil (WCO) can be used as feedstock for biodiesel production. In this project, techno-economic analyses were performed on the biodiesel production in Hong Kong using WCO as a feedstock. Three different catalysts such as acid, base, and lipase were evaluated for the biodiesel production from WCO. These economic analyses were then compared to determine the most cost-effective method for the biodiesel production. The internal rate of return (IRR) sensitivity analyses on the WCO price and biodiesel price variation are performed. Acid was found to be the most cost-effective catalyst for the biodiesel production; whereas, lipase was the most expensive catalyst for biodiesel production. In the IRR sensitivity analyses, the acid catalyst can also acquire acceptable IRR despite the variation of the WCO and biodiesel prices. Full article
(This article belongs to the Special Issue Green Chemistry and the Biorefinery)
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